colSd <- function(X, na.rm=FALSE) apply(X, 2, sd, na.rm=na.rm)
colMax <- function(X, na.rm=FALSE) apply(X, 2, max, na.rm=na.rm)
colMin <- function(X, na.rm=FALSE) apply(X, 2, min, na.rm=na.rm)
colMedian <- function(X, na.rm=FALSE) apply(X,2,median, na.rm=na.rm)